Process for producing substantially pure dermatan sulfate and heparan sulfate glycosaminoglycans, and pharmaceutical use thereof

Abstract

 Substantially pure dermatan sulfate and heparan sulfate are produced starting from a mixture of mucopolysaccharides on an industrial scale by means of a process of precipitation involving saline substances and enzymatic purification. Heparan sulfate shows selective fibrinolytic activity when administered orally, and dermatan sulfate shows antiedemigenic, local anti - congestive and healing activity in topical administration.

Description

Specification

[0001] The present invention refers to a process for the preparation of mucopolysaccharides, and in particular of glycosamino glycans and even more particularly of heparan sulfate and dermatan sulfate (also called chondroitin sulfate B) in a substatially pure state, that is, non contaminated by other families of mucopolysaccharides. The process is advantageously suited to application on an industrial scale.

[0002] The invention also refers to the therapeutic relization of the products obtained with said process.

[0003] Heparan sulfate shows a specific fibrinolytic activity, free of any anti-coagulant and anti-platelet effects, when administered orally.

[0004] Dermatan sulfate shows anti-edematous, local anticongestive and tissue healing activity when applied topically.

[0005] The process according to the invention is of interest since it allows industrial production of mucopolysaccharides in general, including heparin.

[0006] Preparation and purification of glycosaminoqlycans (GAG) according to previous methods was difficult and expensive, could only be carried out in small quantities, in the laboratory.

[0007] The process according to the present invention is of particular interest since it allows the GAG to be extracted in a reproducible fashion on an industrial scale from a mixture containing it in variable proportions, for example obtained in a known way from organs of connective or vascularized tissue, acting essentially on chimico-physical and biological parameters. The process of the present invention is based on the precipitation of GAG by saline substances, varying the selectivity of the precipitation by adjusting the temperature at which it is run. In this way, the precipitates obtained contain the product compounds, contaminated with only small quantities of by - product contaminants.

[0008] These contaminants are removed by means of enzymatic or chemical breakdown treatment, already known in the literature, specific for them. This treatment could not be used on the starting mixture because of the high cost due to the large quantities of GAG which must be broken down, but may be applied advantageously in this case given the minimum quantity of enzyme required for the precipitates mentioned above.

[0009] The process according to the invention will be described below on the basis of which this purification and separation from contaminants is carried out. Clearly however, variations are possible in the process in ways obvious to experts in the field, which still fit into the present invention.

[0010] The starting material consists of an aqueous solution of GAG containing a mixture of various families of GAG in concentrations ranging from 10 to 200 g/liter. An ionizable and water- soluble salt is added to this solution, with ammonium or potassium ion as the cation.

[0011] Examples of salts which may be used according to the invention include potassium acetate, potassium chloride, ammonium sulfate, ammonium acetate, potassium sulfate or similar-salts, organic or inorganic in nature.

[0012] The quantity of salt added must be near the saturation concentration of the salt in water at 25^oC, without reaching the saturation point.

[0013] Said saturation may therefore range from 70 to 90%, preferably 80%.

[0014] The salt may be added in aqueous solution or in its pure state.

[0015] The solution is allowed to rest at room temperature, typically for a 48 hour period, so as to obtain a first precipitate.

[0016] This first precipitate consists almost entirely of dermatan sulfate in a substantially pure state.

[0017] The precipitate is then separated from the liquid, for example by means of filtration, and used to prepare the dermatan sulfate, as described below.

[0018] The clear filtrate is then cooled to a temperature of approximately O°C and left to rest, for example for another 48 hours.

[0019] In this way, most of the chondroitin sulfate A is precipitated, along with any other mucopolysaccharides.

[0020] This second precipitate is separated from the solution, for example by filtration, and discarded. Alternatively it may be used to prepare other-mucopolysaccharides.

[0021] The liquid containing the GAG still in solution is then subjected to a desalinification operation to eliminate the salt which was added at the beginning of the process. This operation may be carried out by means of one or more of the techniques already known for this, of a chemicophysical nature, such as dialysis, precipitation with solvents, ultrafiltration, and the like.

[0022] The desalinified solution is then dehydrated using a suitable process, for example by means of evaporation under vacuum, and the resulting solid, consisting essentially of heparan sulfate contaminated with residual dermatan sulfate and chondroitin sulfate A, is treated with a specific chemical or enzymatic treatment to eliminate said contaminants. Bacterial enzymes are used for this purpose, particularly the chondroitinase ABC. In this way, chondroitin sulfate A and B contaminates are removed.

[0023] Once the breakdown process is complete, the highly purified heparan:;sulfate is released from the hydrolysis products by one of the many techniques available to experts in the field, and is then precipitated and dried by treatment with dehydrating agents, preparing in this way the heparan sulfate according to the invention.

[0024] The first precipitate described above is already practically pure dermatan sulfate. This precipitate is taken up in water containing the precipitating salt introduced at the beginning the process, and is separated by means of a known process such as dialysis, precipitation with solvents, ultrafiltration, etc..

[0025] The second precipitate obtained on cooling the solution to O^OC consists essentially of chondroitin sulfate A

[0026] As mentioned above, from this precipitate one can prepare all the other known mucopolysaccharides included in said precipitate, including heparin.

[0027] The degree of purity of the products of the process according to the invention, heparan sulfate and dermatan sulfate, is controlled by means of a highly sensitive and selective electrophoretic method which can detect any GAG contaminants in concentrations below one part per thousand.

Pharmacological application

[0028] The mucopolysaccharide complex has been used therapeutically for some time, with its anticoagulant and clarifying activity.

[0029] These activities are directly related to the heparin - like action of mucopolysaccharides or GAG.

[0030] Consistent with this action is the GAG activation of ant_ithrombin III.

[0031] No direct action by heparin and the GAG complex has been observed toward fibrinolysis.

[0032] The preparation of these compounds in a substantially pure state has allowed the discovery of previously unknown pharmaceutical activity for henaran sulfate and dermatan sulfate.

Heparan sulfate

[0033] In vitro studies of fibrinolytic activity with Astrup's fibrin platelet method reveal a direct lytic effect when the fibrin contains plasminogen (presence of lysis halo).

[0034] Fibrinolytic activity has been confirmed in vivo as well in rabbits, using the method of measuring the FDP (fibrogen dgradation products), Staphylococcal clumping test, after oral and parenteral administration.

[0035] Intravenous administration of 1 mg/kg has a rapid fibrinolytic effect comparable to that of 2.150 I.U. of urokinase per kilgram.

[0036] Orad administration of a dose between 1 and 30 mg/kg leads to significant increases in serum levels of fibrogen degradation products; in particular this effect is observed at a relatively low dosage level which is in any case insufficient for this administration route for inducing the known effects of the mucopolysaccharide complex, that is, the anticoagulant and clarifying effects; therefore oral treatment with he^paran sulfate is specific for activation of the fibrinolytic system.

[0037] Clinical pharmocology studies confirmed the effectiveness of oral treatment on activation of the fibrinolytic process.

[0038] Heparan sulfate, experimental pharmacology

[0039] Experimental tests in vitro have shown the fibrinolytic action of heparan sulfate. The tests were conducted using the modified Fearnley method, as well as.the fibrin platelet method according to Astrup. In the former, the capacity of the previously incubated substance to induce lysis of a coagulum of dilute mouse blood was demonstrated, experimentally formed by adding thrombin. The second case demonstrated a lytic action on fibrin platelets in the presence of a plasminogen, on which the substance shows activation at a concentration of 100 mg/ml comparable to the activity of a 25 - 50 I.U./ml dose of urokinase.

[0040] In vivo tests were performed designed to show activation of fibrinolysis in New Zealand rabbits of both sexes treated intravenously and intraduodenally (with tying of the pylorus) at doses ranging respectively from 0,5 - 1 and 1 - 30 mg/kg for the two administration routes.

[0041] These tests showed that intravenous treatment at a dose of 1mg/kg had a clear fibrinolytic effect after 3₀ minutes which was maintained until 180 minutes after administration, inhibiting platelet aggregation due to ADP, collagen, thrombin; it acted as an anticoagulant and clarifier of plasmatic lipids.

[0042] Oral treatment (intraduodenal), on the other hand, was shown to be significantly effective and selective only in the activation of fibrinolysis; this effect aooears at 1 - 10 mg/kg doses of heparan sulfate 6 hours after treatment, and is highly significant at the 30 mg/kg after 2 hours. It is dissociated from the anticoagulant or clarifying effect.

[0043] However, in terms of the ends established for therapeutic use, it should be noted that oral tratment up to a 10 mg/kg dose has a significant fibrinolytic effect with no-anti-coagulant activity; the latter is seen when the compound is administered parenterally.

[0044] Clinical pharmacology studies with patients suffering from venopathy and arteripathy in general, treated orally in a gastro-resistant fashion with doses from 200 - 600 mg/day, revealed a specificity of the fibrinolytic effect for this administration route, documented in the laboratory as well as in therapy.

[0045] In fact laboratory studies show a significant increase in serum FDP, an increase in plasma fibrinogen and plasminogen consumption, and considerably reduced euglobulin lysis times, while no variation is seen in the parameters involved in the coagulative and aggregative process and in the lipid level.

[0046] From a therapeutic point of view, all the phenomena are observed which indicate regression of a preformed thrombus, achieving clinical cure in many cases.

Dermatan sulfate

[0047] _Dermatan sulfate,or chondroitin sulfate B, is contained in large amounts in connective tissue, and in particular in fibrous connective tissue; its presence is related to the evolution in a fibrous direction of primitive connective tissue reticular in character.

[0048] When the connective tissue tends to assume aspects of more advanced stages, dermatan sulfate tends to decrease.

[0049] Evolution of the fibrillary order itself of the granulation tissue toward a fibrous organization, and thus toward cicatrical tissue, is also accompanied by a considerable increase in chondroitin sulfate B content.

[0050] This mucopolysaccharide is thought to be implicated in the formation of collagen and elastic fibrills, as well as important in the formation of the amorphous substance present between the collagen fibers.

[0051] Therefore, dermatan sulfate is a mucopolysaecharide closely correlated to the formation and evolution of collagen tissue and so to the function this tissue performs.

Dermatan sulfate, pharmacological properties

[0052] In vivo pharmacoligical studies in test animals have shown that dermatan sulfate in a preparation for topical use administered cutanuously to rabbits, effects local pharmacological action characteristic of this mucopolysaccharide family.

Antiedemigen and local anticongestive activity

[0053] It is known that acute dermatitis experimentally induced by UV rays faithfully simulates the general conditions of tissue inflammation and necrosis which are always accompanied by trophic and microcirculatory disturbances as well as by edematous congestion in the surrounding area.

[0054] It has been shown that the substance, when applied repeatedly to rabbit skin, exhibits protective activity toward dermatitis induced by repeated radiation.

[0055] New Zealand rabbits of both sexes were used, divided.into a control group, a group treated with placebo (excipient) and a third group treated with the preparation of dermatan sulfate for topical use.

[0056] The rabbits were treated with a depilatory in a certain lateral dorsal area followed three days later by the first treatment with 1 g of the preparation; it was administered twice daily for 8 days consecutively, for a total dose of 2 g per rabbit/day.

[0057] Three hours after the daily treatment all the animals were subjected to UV radiation on said skin area in a completely standardized manner; the thickness of the skin intthe area involved was also measured daily before the radiation. Four days after the end of treatment, the animals were sacrificed; the irradiated areas of the skin taken and fixed in buffered isotonic formalin.

[0058] The study showed clearly that treatment with dermatan sulfate has a significant trophic, anticongestive and antiedemigenic effect toward dermatitis induced by UV radiation, while the placebo preparation had no effect on the parameters considered.

[0059] In fact histological examination showed that while the control animals and the group treated with placebo exhibited the same degree of wrinkling and thinning of the skin, associated with mild glandular atrophy and occasional inflammatory infiltrates in the derma, the animals treated with dermatan sulfate showed no cutaneous alteration.

Action on healing of a surgical wound

[0060] New Zealand rabbits divided into a non - treated control group, a group treated with placebo and a group treated with dermatan sulfate were first depilated in the interscapular area and anesthetized locally with lidocain; a 1 cm² area of skin was then removed surgically.

[0061] The placebo and the active principle preparations were applied, in quantities corresponding to 0.333 g/kg of preparation, two hours apart under aseptic conditions every 24 hours for 10 days. The condition of the wound was checked daily, and at the end all the animals were subjected to scheduled death. The skin area was-,removed along with the corresponding connective area of the subcutaneous layer.

[0062] The tissue sample was placed in buffered isotonic formalin solution and examined histologically after hematoxylin - eosin staining.

[0063] The daily observation of the wound and the relative reparative - healing processes showed reduced thickness of the edges of the wound, inproved trophism and reduced closing times for the edges of the wound in the animals treated with dermatan sulfate with respect to those treated with excipient only and to the controls.

[0064] Histological examination of the control animals showed a condition of chronic and sclerosic lesion with thick and fibrotic cicatricial connective tissue, with the edges of the wound affected by hyperkeratosis and acanthosis. The animals treated with placebo showed a completely analogous picture. Treatment with dermatan sulfate on the other hand prevented chronic and sclerosic lesions, fibrotic thickening of the cicatricial connective tissue and acanthosis of the edges of the wound.

Clinical-pharmacology

[0065] Dermatan sulfate was tested in preparations for topical use on patients with superficial lesions involving the cutaneous and subcutaneous layer, with various degrees of ulceration and with varying difficulty in healing (in some cases due to association with metabolic disturbances related to collogen synthesis).

[0066] Treatment was administered under strictly aseptic conditions, repeated twice daily, for a variable length of time depending on the lesion, in comparison with another group of patients treated under the same conditions with a placebo preparation. The patients treated with dermatan sulfate showed more rapid healing (30% reduction in the time required for the edges of the lesion to close) and better development of connective :icatricial tissue, as well as improvement in the macroscopic condition of the tissue after the repair process: absence of fibrous evolution, telangiectasis and pigmentation of the cicatricial tissue in the cases treated with the test substance, although these signs were always present in the group treated with placebo.

[0067] Therefore, the object of the present invention is pharmaceutical compositions containing heparan sulfate as the active fibrinolytic agent, prepared by means of the process according to the invention, administered in an oral dose of 1 - 30 mg/kg daily.

[0068] The object of the present invention is also pharmaceutical compositions for topical use, containing dermatan sulfate as active anti-edemigenic, local anti-congestive and healing agent, prepared by means of the nrocess according to the invention.

Claims

1. Process for producing substantially pure dermatan sulfate and heparan sulfate, starting from a mixture of mucopolysaccharides in aqueous solution which contains them, characterized by operations of:

a) introducing in said starting solution a water soluble ionizing salt'consisting of ammonium or potassium as the cation part, up to a concentration of 70 - 90% of the saturation level of said salt at 25°C, so as to produce at room temperature a first precipitate containing dermatan sulfate in a substantially pure state;

b) separating said precipitate from the solution and recovering the substantially pure dermatan sulfate as first product;

c) cooling the solution removed from the precipitate to approximately O°C in order to produce a second precipitate at said temperature containing chondroitin sulfate A;

d) removing said second precipitate from the solution;

e) separating from the residual solution the salt introduced in operation (a) so as to prepare a desalinified solution;

f) removing the water from said desalinified solution so as to prepare a solid containing heparan sulfate contaminated with other glycosaminiglycanes;

g) subjecting said solid to enzymatic treatment with

pndroitinase ABC, so as to eliminate said impurities and recover the heparan sulfate substantially pure as second product.

2. Process according to claim 1, in which said salt is protassium acetate, ammonium chloride, ammonium acetate or potassium sulfate.

3. process according to claim 1, in which said concentration in operation (a) is 80% of the saturation concentration at 25°C.

4. Frocess according to claim 1, in which said separation operation (e) is an operation of d&alysis, precipitation with solvents, ultrafiltration and the like.

5. Substantially pure dermatan sulfate obtained by means of the process claimed in claim 1.

6. Substantially pure heparan sulfate obtained by means of the process claimed in claim 1.

7. Active fibrinolytic agent consisting of heparan sulfate as claimed in claim 6, when administered orally in a dose of 1 - 30 mg/kg/day.

8. Pharmaceutical composition for oral administration, containing a quantity effective for fibrinolytic activity of heparan sulfate as claimed in claim 6, as well as pharmacologically compatible excipients.

9. Active antiedemigenic, local anti-congestive and healing agent consisting of dermatan sulfate as claimed in claim 5.

10. Pharmaceutical composition for topical use containing a quantity effective for the anti - edemigenic, anti - congestive and healing activity of dermatan sulfate as claimed in claim 5, as well as pharmacologically compatible excipients.